1. Field of the Invention
This invention is concerned with the resolution of water-bituminous emulsions stabilized with clay by treatment with polyethylene oxide; a hydrocarbon diluent and subsequently with sodium hydroxide serving as a secondary bitumen clean up chemical. The invention is also concerned with the separation of water from bitumen which has been brought to the surface in the form of oil-in-water-emulsions by an in-situ recovery process.
2. Prior Disclosures
Numerous hot water extraction methods exist for separating crude oil from bituminous sands (tar sands, oil sands and the like) which involve mixing such sands with hot or cold water and separating the sand from the resulting emulsions.
The technical difficulty encountered with emulsions produced by in-situ operations is that the liquid mixture is a highly stabilized emulsion which is difficult to break with standard treating chemicals.
Previous attempts to break emulsions resulting from hot water extraction processes are illustrated, inter alia, by the techniques described in U.S. Pat. Nos. 3,808,120, 3,607,721, and 3,487,003.
Thus, U.S. Pat. No. 3,808,120 describes a method for separating at least water and solids from the froth produced in a hot water process of separating bitumen from tar sands by treating the froth in at least one cyclone zone, after which it is treated in at least two centrifuging zones.
In U.S. Pat. No. 3,607,721 a process for the removal of solids and emulsified water from the bituminous emulsion is disclosed which comprises diluting the emulsion with a hydrocarbon diluent; maintaining the resulting mixture in a settling zone; removing the emulsion when substantially free of solids and emulsified water from the top of the settling zone; withdrawing settled sludge from the bottom of the settling zone and centrifuging the withdrawn sludge to separate bitumen and diluent from the settled solids and the emulsified water.
U.S. Pat. No. 3,487,003 describes a method for reducing the solids content of an effluent discharge from a hot water process for separating oil from bituminous sands by adding a flocculating agent which may be organic, inorganic or even a polyalkylene oxide of undisclosed molecular weight to this effluent; adjusting the pH of the effluent to less than 7.5 or more than 9 to effect flocculation of at least a portion of the solids therein; centrifuging the effluent now containing flocculated solids and recovering the effluent discharge substantially reduced in solids content. This method treats not an oil-in-water emulsion but rather an effluent comprised of the effluent from the sand tailing layer and the middlings layer. Further, there is no appreciation therein of the necessity for maintaining the temperature within a given range during treatment with the flocculating agent.
U.S. Pat. No. 2,964,478 describes a process for breaking an oil-in-water emulsion by subjecting the emulsion to the sole action of a polyalkylene oxide having a molecular weight of 100,000 to 3 million. In the practice of that process the mixture of the resin is allowed to stand quiescent for about 19 hours at a settling temperature ranging from room temperature to 160.degree., after which some of the oil rises to the surface of the pond or sump and is removed.
In U.S. Pat. No. 4,058,453 to Patel et al, there is disclosed a process for recovering oil from oil-in-water and water-in-oil emulsions by demulsifying the emulsions by adding thereto effective amounts of non-ionic, water-soluble polyethylene oxide polymers having a molecular weight in the range of 100,000 to 7,000,000, called "Polyox" and a calcium chloride and separating the oil from the water. Optionally in that process, the emulsions are diluted, following addition to the polymer, with from 30 to 50 volume percent of a hydrocarbon diluent and, after maintaining the temperature of the resulting mixture at between 150.degree. and 210.degree. F., the oil therein is centrifuged from the solids and the water.